Plant and Animal Cells

Cell Oraganelles

The difference between plant cells and animal cells, is that; plant cells have Cell walls, Chloroplasts and Vacuole. Animals don't, But both Plant and Animal Cells have a Nucleus, Cytoplasm, Mitochondria, Ribosomes and a Cell Membrane.

Nucleus - Containing chromosomes made of genes. Controls the activities of the cell. Cytoplasm - Where metabolic reactions controlled by enzymes take place. Mitochondrion - Where energy is released in respiration.

Ribosomes - Where Protein Synthesis takes place.

Cell Membrane - Controls the passage of substances in and out of the cell.

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Microbial Cells

Yeast is a single-celled fungus. Its cells have cell walls but they are not made of cellulose like plants cell walls. Fungi can not photosynthesise as they have no chloroplasts.

Algae are simple, plant-like organisms. Their cells are similar to plant cells.

Fungal Cells: They are very similar to plant cells but their cell wall is not made from celluose and the vacuole is smaller.

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Electron Mircoscopes and Viruses

Electron Mircoscopes used in research labs, can magnify an object up to two million times, this makes it easy for them to studies viruses.

Viruses are not made of cells therefore do not have cell membrane, nucleus etc. Most viruses are made up of a sphere of protein with DNA inside it. This DNA is forceful inserted into host cells allow the virus to take over the cell. Viruses are a 100 times smaller than DNA.

Examples of viruses is Influenza (Flu) and the common cold. Viruses can only reproduce inside host cells, and they damage the cell when they do this. A virus can get inside a cell and, once there, take over and make hundreds of thousands of copies of itself. Eventually the virus copies fill the whole host cell and burst it open. The viruses are then passed out in the bloodstream, the airways, or by other routes.

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Specialised Cells

The human body contains hundreds of different kinds of specialised cells.

Examples of these are :

Red blood cells

Goblet cells

Ciliated cells

Specialised plant cells

Root-hair cells are specialised plant cells

They are fine hair-like extensions of a root

Their large surface area enables plants to maximise their asorption of water from the soil.

All the different types of specialised cell are the result of differentiation during the growth of the organism.

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How specific cells are specialised

Sperm Cells are specialised in a number of ways. They have an Undulipodium (tail) which moves by energy generated by many mitochondria and propels the cell. The head of the cell contains an Acrosome, which is a specialised Lysosome that releases enzymes so that the Sperm Cell can penetrate the Ovum Coat of the Egg.

Red blood cells - Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of haemoglobin.

The palisade cell - palisade cell is tall with a large surface area
It's found on the top side of a leaf - ideal for good absorption of carbon dioxide and light - both are needed for photosynthesis. They're packed with chloroplasts, which contain the green pigment chlorophyll, which is needed for photosynthesis.

Cilia cells line all the air passages in your lungs, they have tiny hairs, which filter the air as it blows through. The hairs sweep mucus (snot) with trapped dust and bacteria up to the back of the throat where it is swallowed.

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Diffusion

Diffusion is the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region where they are of a higher concentration, into a region where they are in a lower concentration.

Most cells need oxygen so that they can respire. oxygen diffuses into the cells from a higher concentration outside to a lower concentration inside.

The concentration of oxygen insisde the a cell is kept low because keeps on using it up.

The speed of diffusion can be increased by increasing the difference in concentration (the concentration gradient) and increasing the temperature. (the faster that the particles move around, the fast they will diffuse.)